JP6129336B2 - Semiconductor wetting agent and polishing composition - Google Patents

Description

This application is a related application of Japanese Patent Application No. 2013-231752, which is a Japanese patent application filed on November 8, 2013, and claims priority based on this Japanese application. All the contents described in this Japanese application are incorporated herein by reference.
The present invention relates to a wetting agent for semiconductors and a polishing composition, and more particularly to a wetting agent for semiconductors and a polishing composition used for final polishing of a silicon wafer.

  Semiconductor devices using a silicon wafer as a substrate are widely used in information communication devices such as personal computers and mobile phones, and digital home appliances such as digital cameras and televisions. As semiconductor chips have been highly integrated and increased in capacity in recent years, the processing accuracy of semiconductor devices has been continually miniaturized. Wafers prior to device formation have defects such as smoothness and scratches. The so-called intactness requirement that does not exist is becoming increasingly severe.

As a wafer smoothing technique, a polishing process called CMP (Chemical Mechanical Polishing) is often used. In the smoothing treatment by CMP, a polishing composition containing fine abrasive grains and a basic compound is used. While supplying this polishing composition to the surface of the polishing pad, the surface is polished by relatively moving the polishing pad in pressure contact with the wafer as the object to be polished. At this time, since the mechanical polishing by the abrasive grains and the chemical polishing by the basic compound proceed simultaneously, the wafer surface can be smoothed over a wide range with high accuracy.
Generally, in wafer polishing by CMP, high-precision smoothing is realized by performing polishing in 3 to 4 stages. In primary polishing and secondary polishing performed in the first stage and the second stage, since the main purpose is to smooth the surface, the polishing rate tends to be regarded as important. On the other hand, in the final polishing in the third stage or the fourth stage, the haze and COP (Crystal Originated Particles) of the wafer surface are suppressed, and further, agglomerated abrasive grains, polishing pad debris, and polishing are removed. Emphasis is also placed on the prevention of contamination caused by the adhesion of so-called particles such as silicon powder.

  As a polishing composition used for the above-mentioned finish polishing, it is known that a method of adding a water-soluble polymer compound to the polishing composition is effective. Patent Document 1 discloses a polishing composition comprising a water-soluble polymer compound having a molecular weight of 100,000 or more and water-soluble salts. Patent Document 2 discloses a polishing composition containing a specific polyacrylamide derivative. Furthermore, Patent Document 3 describes a polishing composition containing a water-soluble polymer compound, and describes that a cellulose derivative or polyvinyl alcohol can be used as the water-soluble polymer compound.

Japanese Patent Laid-Open No. 2-158684 Japanese Patent No. 4915736 JP 11-116942 A

However, in the invention described in Patent Document 1, the water-soluble polymer compound used is not sufficiently adsorbed to the wafer surface, and the haze and COP of the wafer surface after finish polishing are not satisfactory. Also, water-soluble salts added for the purpose of improving the polishing properties are not preferable from the viewpoint of dispersibility of the silica abrasive grains. If the dispersibility of the silica abrasive grains is insufficient, the surface roughness of the wafer surface after finish polishing tends to increase, and problems such as scratches tend to occur.
In addition, Patent Document 2 discloses only a homopolymer of N, N-dimethylacrylamide in the Examples as a specific example of the polyacrylamide derivative, but the dispersibility of the abrasive grains is not sufficient. . For this reason, problems such as insufficient smoothness of the wafer surface after finish polishing and scratches are likely to occur.
Similarly, the cellulose derivative or polyvinyl alcohol described in Patent Document 3 is not sufficiently adsorbable on the wafer surface. In addition, in the Example of Patent Document 2, an experimental example using hydroxyethyl cellulose as a specific water-soluble polymer compound is disclosed, but since it is a compound derived from a natural product, there is a problem in that quality variation is large. There was also.

  The present invention has been made in view of such circumstances, and provides a wetting agent for semiconductor and a polishing composition effective in smoothing the wafer surface with high accuracy and effective in suppressing COP in surface polishing of a silicon wafer. It is an object to do.

  As a result of intensive studies to solve the above problems, the present inventors include a water-soluble polymer having a structural unit derived from N- (meth) acryloylmorpholine as a main component and having substantially no cationic group. It has been found that the use of a wetting agent for semiconductors has an effect on smoothing the wafer surface after polishing and suppressing COP, and the present invention has been completed.

The present invention is as follows.
[1] A wetting agent for semiconductor containing a water-soluble polymer having 50 to 100 mol% of a structural unit derived from N- (meth) acryloylmorpholine and substantially free of a cationic group.
[2] The wetting agent for semiconductors according to [1], wherein the structural unit derived from the N- (meth) acryloylmorpholine is 100 mol%.
[3] The semiconductor wetting agent as described in [1] or [2] above, wherein the water-soluble polymer has a number average molecular weight in the range of 1,000 to 300,000.
[4] The method for producing a water-soluble polymer according to any one of [1] to [3], wherein a nonionic and / or anionic polymerization initiator is used as a polymerization initiator, and N- ( A method for producing a water-soluble polymer, comprising radically polymerizing 50 to 100 mol% of (meth) acryloylmorpholine and 0 to 50 mol% of another monomer.
[5] A polishing composition comprising the semiconductor wetting agent according to any one of [1] to [3], water, abrasive grains, and an alkali compound.
[6] A method of polishing a silicon wafer using a water-soluble polymer having 50 to 100 mol% of structural units derived from N- (meth) acryloylmorpholine and substantially free of a cationic group.

  The wetting agent for semiconductors of the present invention has excellent adsorptivity to the wafer surface after polishing. For this reason, by using the polishing composition containing the semiconductor wetting agent, it is possible to increase the smoothness of the polished wafer surface and to suppress the COP because of excellent etching resistance. Furthermore, since the dispersibility of silica is also good, there are few scratches and surface roughness due to the agglomerated silica abrasive grains, and a wafer surface with excellent scratch resistance can be obtained.

  Hereinafter, representative and non-limiting specific examples of the present disclosure will be described in detail. This detailed description is intended merely to provide those skilled in the art with details for practicing the preferred embodiments of the present invention and is not intended to limit the scope of the present disclosure. Also, the additional features and inventions disclosed below can be used separately from or together with other features and inventions to provide further improved semiconductor wetting agents and polishing compositions.

  Further, the combinations of features and steps disclosed in the following detailed description are not essential in carrying out the present disclosure in the broadest sense, and are particularly only for explaining representative specific examples of the present disclosure. It is described. Moreover, various features of the representative embodiments described above and below, as well as those described in the independent and dependent claims, are described herein in providing additional and useful embodiments of the present disclosure. They do not have to be combined in the specific examples given or in the order listed.

  All features described in this specification and / or claims, apart from the configuration of the features described in the examples and / or claims, are individually disclosed as limitations on the original disclosure and claimed specific matters. And are intended to be disclosed independently of each other. Further, all numerical ranges and group or group descriptions are intended to disclose intermediate configurations thereof as a limitation to the original disclosure and claimed subject matter.

  The present invention will be described in detail below. In the present specification, “(meth) acryl” means acryl and methacryl, and “(meth) acrylate” means acrylate and methacrylate. The “(meth) acryloyl group” means an acryloyl group and a methacryloyl group.

<Water-soluble polymer>
The wetting agent for semiconductor of the present invention contains a water-soluble polymer having 50 to 100 mol% of structural units derived from N- (meth) acryloylmorpholine and substantially free of a cationic group. The structural unit derived from N- (meth) acryloylmorpholine is preferably in the range of 70 to 100 mol%, more preferably in the range of 90 to 100 mol%, and most preferably 100 mol%.
The structural unit derived from N- (meth) acryloylmorpholine has good adsorptivity to the wafer surface and excellent hydrolysis resistance. Therefore, the wetting agent for semiconductors containing a water-soluble polymer mainly composed of the structural unit exhibits excellent alkali resistance even when a polishing composition is formed with an alkali compound or the like, and the polishing composition The object exhibits good etching resistance.

In the present invention, in addition to N- (meth) acryloylmorpholine, other monomers copolymerizable therewith may be used. Other monomers are not particularly limited. For example, (meth) methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate (meta) ) Acrylic acid alkyl esters; Unsaturated acids such as (meth) acrylic acid, crotonic acid, maleic acid, itaconic acid and fumaric acid and their alkyl esters; Unsaturated acid anhydrides such as maleic anhydride; 2-acrylamide 2-sulfonic acid group-containing monomers such as 2-methylpropanesulfonic acid and salts thereof; methyl (meth) acrylamide, ethyl (meth) acrylamide, n-propyl (meth) acrylamide, isopropyl (meth) acrylamide, n-butyl ( N-Al such as (meth) acrylamide and 2-ethylhexyl (meth) acrylamide (Di) alkylaminoalkylamides such as methyl (amino) amide; methylaminopropyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, ethylaminopropyl (meth) acrylamide and diethylaminopropyl (meth) acrylamide; (Di) alkylaminoalkyl (meth) acrylates such as (meth) acrylate, dimethylaminoethyl (meth) acrylate, ethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate; styrene, vinyltoluene and vinylxylene Aromatic vinyl compounds; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, iso Alkyl vinyl ethers having an alkyl group having 1 to 10 carbon atoms such as til vinyl ether, t-butyl vinyl ether, n-hexyl vinyl ether, 2-ethylhexyl vinyl ether, n-octyl vinyl ether, n-nonyl vinyl ether and n-decyl vinyl ether; vinyl formate , Vinyl ester compounds such as vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl piperate and vinyl versatate; α- such as ethylene, propylene and butylene Examples thereof include olefins, and one or more of these can be used.
The amount of these monomers used in the water-soluble polymer is in the range of 0 to 50 mol%, preferably in the range of 0 to 30 mol%, and more preferably in the range of 0 to 10 mol%. If the amount of other monomers used exceeds 50 mol%, the amount of N- (meth) acryloylmorpholine used is less than 50 mol%, so that the adsorptivity to the wafer is not sufficient, and the wetting for semiconductors of the present invention. The effect of the agent may not be obtained.

  The water-soluble polymer of the present invention is substantially free of a cationic group. Since the cationic group is introduced by a monomer having a cationic group such as a quaternary ammonium base, an initiator, or the like, in the present invention, “substantially does not contain a cationic group” means that these components are raw materials. Means not using as.

  The number average molecular weight (Mn) of the water-soluble polymer is preferably in the range of 1,000 to 300,000, more preferably in the range of 1,500 to 150,000, and still more preferably in the range of 2,000 to The range is 100,000. If the number average molecular weight (Mn) is 1,000 or more, the wettability of the wafer is sufficiently secured, and if it is 300,000 or less, the dispersibility of the abrasive grains can be secured. The number average molecular weight can be measured by polystyrene conversion using GPC (gel permeation chromatography, for example, HLC-8220, manufactured by Tosoh Corporation).

  Further, the molecular weight distribution (PDI) of the water-soluble polymer is preferably narrow. Specifically, the value obtained by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn) is preferably 4.0 or less, more preferably 3.5 or less, and 3.0 or less. More preferably. When the molecular weight distribution (PDI) is 4.0 or less, sufficient wettability is exhibited, and deterioration in dispersibility of (silica) abrasive grains caused by a high molecular weight body can be avoided.

<Method for producing water-soluble polymer>
The water-soluble polymer in the present invention uses a nonionic and / or anionic polymerization initiator as a polymerization initiator in a polymerization solvent, N- (meth) acryloylmorpholine 50 to 100 mol%, and other monomers 0 It can be obtained by radical polymerization of ˜50 mol%.

  The polymerization method is not particularly limited, but the solution polymerization method is preferable in that a water-soluble polymer can be obtained in a uniform state. As the polymerization solvent in the solution polymerization, water or a mixed solvent composed of water and an organic solvent can be used. Specific examples of the organic solvent include methanol, ethanol, isopropanol, acetone, and methyl ethyl ketone, and one or more of these may be used in combination. Among the above, it is preferable to employ an aqueous solution polymerization method using water as a polymerization solvent.

In the polymerization, any known nonionic and / or anionic polymerization initiator may be used, and a radical polymerization initiator is particularly preferably used.
Examples of the radical polymerization initiator include persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate, hydroperoxides such as t-butyl hydroperoxide, water-soluble peroxides such as hydrogen peroxide, and methyl ethyl ketone. Ketone peroxides such as peroxide and cyclohexanone peroxide, dialkyl peroxides such as di-t-butyl peroxide and t-butylcumyl peroxide, t-butyl peroxypivalate, t-hexyl peroxypivalate, etc. Oil-soluble peroxides such as peroxyesters, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate, 2,2′-azobis [2- ( 2-Imidazolin-2-yl) propane], 2,2′-azobis [2- Water-soluble azo compounds such as til-N- (2-hydroxyethyl) propionamide] and 4,4′-azobis-4-cyanovaleric acid, 2,2′-azobisisobutyronitrile, 2,2′- Examples thereof include oil-soluble azo compounds such as azobis (2,4-dimethylvaleronitrile) and 2,2′-azobis (2-methylbutyronitrile).
The radical polymerization initiator may be used alone or in combination of two or more.
Among the radical polymerization initiators, persulfates and water-soluble azo compounds are preferable, and water-soluble azo compounds are particularly preferable because the polymerization reaction can be easily controlled.
The ratio of the radical polymerization initiator used is not particularly limited, but is preferably 0.1 to 10% by mass based on the total weight of all monomers constituting the entire water-soluble polymer. A ratio of 1 to 5% by mass is more preferable, and a ratio of 0.2 to 3% by mass is more preferable.

The polymerization of the water-soluble polymer may be carried out in the presence of a chain transfer agent as necessary. By using a chain transfer agent, the molecular weight of the water-soluble polymer can be appropriately adjusted.
As the chain transfer agent, known ones can be used. Specifically, ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol, 2-butanethiol, 1-hexanethiol, 2-hexane Thiol, 2-methylheptane-2-thiol, 2-butylbutane-1-thiol, 1,1-dimethyl-1-pentanethiol, 1-octanethiol, 2-octanethiol, 1-decanethiol, 3-decanethiol, 1-undecanethiol, 1-dodecanethiol, 2-dodecanethiol, 1-tridecanethiol, 1-tetradecanethiol, 3-methyl-3-undecanethiol, 5-ethyl-5-decanethiol, tert-tetradecanethiol, 1 -Hexadecanethiol, 1-heptadecanethiol and 1- In addition to alkylthiol compounds having an alkyl group of 2 to 20 carbon atoms such as kutadecanethiol, mercaptoacetic acid, mercaptopropionic acid, 2-mercaptoethanol, etc. may be mentioned, and one or more of these may be used Can do.

Among chain transfer agents, an alkylthiol compound having an alkyl group having 2 to 20 carbon atoms is preferable from the viewpoint of good adsorption to a wafer, more preferably an alkyl group having 4 to 20 carbon atoms, and more preferably Those having 6 to 20 alkyl groups are more preferred.
When using a chain transfer agent, the preferable usage-amount is 0.1-10 mass% with respect to the quantity of all the monomers, More preferably, it is 0.5-5 mass%.

  As reaction temperature at the time of superposition | polymerization, 30-100 degreeC is preferable, 40-90 degreeC is more preferable, and 50-80 degreeC is further more preferable.

<Wetting agent for semiconductors>
The semiconductor wetting agent of the present invention comprises the water-soluble polymer and water. It is preferable to use high-purity water so as not to impair the effect as a wetting agent. Specifically, it is preferable to use pure water, ultrapure water, or distilled water from which foreign ions are removed by filtration after removing impurity ions with an ion exchange resin. In addition to this, the wetting agent may contain an organic solvent such as alcohol and ketone having high miscibility with water.
Although the ratio of the water-soluble polymer in the wetting agent for semiconductor is not particularly limited as long as it is a viscosity that can be easily handled as an aqueous solution, the range is preferably 1 to 50% by mass, more preferably 3 to 40% by mass, The range of 30% by mass is more preferable.

The water-soluble polymer in the present invention is excellent in adsorptivity to the wafer surface and the like, and particularly exhibits high adsorptivity to the wafer surface in a state where the oxide film is completely removed. For this reason, when the semiconductor wetting agent of the present invention is used in the wafer surface treatment process, the smoothness of the polished wafer surface can be improved, and contamination caused by COP and particle adhesion can be reduced. The following mechanism is assumed as a reason why these effects can be obtained.
Regarding the smoothness of the wafer surface, the water-soluble polymer in the semiconductor wetting agent is adsorbed on the wafer surface, so that the friction between the wafer surface and the abrasive grains is reduced in the mechanical polishing of CMP. For this reason, it is considered that the minute unevenness formed on the wafer surface by mechanical polishing is reduced and the smoothness is improved.

In addition, as described above, in mechanical polishing, the polishing composition is supplied to the wafer surface and the polishing pad is pressed against the wafer surface and rotated to physically polish the wafer surface. Therefore, the polishing pad is pressed against a portion other than the COP on the wafer surface and polished in a direction perpendicular to the wafer surface. As the mechanical polishing proceeds, the COP gradually decreases, and the COP disappears when the wafer surface is polished beyond the depth. Therefore, it is considered that the mechanical polishing shows the effect of reducing the number of COPs and the size thereof.
On the other hand, in chemical polishing, the polishing composition enters the COP during polishing, and the basic compound corrodes or etches the inside of the COP. As described above, since the polishing is performed in the direction perpendicular to the inner wall of the COP, it is considered that the COP on the wafer surface increases with the progress of chemical polishing.
In the present invention, it is assumed that the water-soluble polymer adsorbed on the wafer surface has a function of suppressing chemical polishing more than mechanical polishing. It is presumed that this tendency becomes stronger as the water-soluble polymer adsorbability to the wafer becomes higher, and as a result, a wafer surface having high smoothness and low COP can be obtained.

  Furthermore, when the water-soluble polymer is adsorbed on the wafer surface, the surface is hydrophilized. Thereby, contamination due to adhesion of particles during polishing can also be prevented.

  The present invention also provides a method for polishing a wafer by adsorbing such a water-soluble polymer to the wafer. As a form in which the water-soluble polymer is adsorbed to the wafer, the water-soluble polymer is supplied as a semiconductor wetting agent containing water-soluble polymer and water, and includes the water-soluble polymer of the present disclosure, water, abrasive grains, and an alkali compound. The form which supplies polishing composition with respect to a wafer is contained.

<Polishing composition>
The polishing composition of the present invention comprises the semiconductor wetting agent, water, abrasive grains, and an alkali compound. The ratio of the semiconductor wetting agent in the polishing composition is not particularly limited, but it is preferable that the polishing composition has an appropriate viscosity for handling in CMP and adsorbing to the wafer surface. The specific viscosity of the polishing composition is preferably in the range of 0.1 to 10 mPa · s, more preferably in the range of 0.3 to 8 mPa · s, and 0.5 to 5 mPa · s. More preferably, it is in the range.
Moreover, it is preferable to use the said water-soluble polymer so that it may become the range of 0.001-10 mass% of the whole composition for abrasive | polishing agents, and it is more preferable that it is the range of 0.005-5 mass%.

  Colloidal silica or the like can be used as the abrasive. When colloidal silica is used as the abrasive, the content in the polishing composition is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, and 3 to 20% by mass. More preferably it is. If the usage-amount of colloidal silica is 0.1 mass% or more, the polishing rate of mechanical polishing will become favorable. Moreover, if it is 50 mass% or less, the dispersibility of an abrasive grain is hold | maintained and the smoothness of a wafer surface can be made favorable.

  The average particle size of the corridal silica is appropriately selected from the required polishing rate and the smoothness of the wafer surface after polishing, but is generally in the range of 2 to 500 nm, preferably in the range of 5 to 300 nm. A range of ˜200 nm is more preferable.

The alkali compound is not particularly limited as long as it is a water-soluble alkali compound, and alkali metal hydroxides, amines, ammonia, quaternary ammonium hydroxide salts, and the like can be used. Examples of the alkali metal hydroxide include potassium hydroxide, sodium hydroxide, rubidium hydroxide and cesium hydroxide. Examples of amines include triethylamine, monoethanolamine, diethanolamine, triethanolamine, diisopropanolamine, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylpentamine, and tetraethylpentamine. Examples of the quaternary ammonium hydroxide salt include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. Among these, ammonia or a quaternary ammonium hydroxide salt is preferable from the viewpoint of less contamination of the semiconductor substrate.
The polishing composition of the present invention is preferably adjusted to have a pH of 8 to 13 by adding the alkali compound. More preferably, the pH range is adjusted to 8.5-12.

  In addition to the above, an organic solvent, various chelating agents, surfactants, and the like can be added to the abrasive composition as necessary.

Hereinafter, the present invention will be specifically described based on examples. In addition, this invention is not limited by these Examples. In the following, “parts” and “%” mean mass parts and mass% unless otherwise specified.
It describes below about the analysis method of the water-soluble polymer obtained by the manufacture example, and the evaluation method of the wetting agent for semiconductors or polishing composition in an Example and a comparative example.

<Molecular weight measurement>
About the polymer obtained by each manufacture example, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by polystyrene conversion using GPC (gel permeation chromatography HLC-8220, product made from Tosoh). Moreover, molecular weight distribution (PDI = Mw / Mn) was computed from the obtained value.

<Etching resistance (E.R.)>
After measuring the weight of the wafer cut to 3 × 6 cm with a glass cutter, it was immersed in a 3% hydrofluoric acid aqueous solution for 20 seconds to remove the oxide film on the wafer surface, and then washed with pure water for 10 seconds. This process was repeated until the wafer surface was completely water repellent. Next, an etching chemical solution was prepared by adding a semiconductor wetting agent to ammonia water having an ammonia: water weight ratio of 1:19 so that the concentration of the water-soluble polymer was 0.18 wt%. The wafer was completely immersed in an etching chemical solution and left to stand at 25 ° C. for 12 hours for etching. From the wafer weight change before and after etching, the etching rate (E.R.) was calculated according to the following formula.

<Wettability>
The oxide film on the wafer surface was removed by the same method as etching resistance, and then immersed in a 0.18 wt% water-soluble polymer solution for 5 minutes. After immersion, the surface of the wafer was pulled up using a tweezers so as to be perpendicular to the liquid level, and the water-repellent distance from the end of the wafer at the time when 10 seconds had passed was visually confirmed, and judged according to the following criteria.
○: Water repellent distance less than 5 mm △: Water repellent distance 5 to 10 mm
×: Water repellent distance> 10mm

<Wafer appearance>
The wafer surface after etching was performed by the same method as the etching resistance was visually confirmed, and judged according to the following criteria.
○: No roughening on the surface △: The surface is slightly rough ×: The surface is extremely rough

<Alkali resistance>
A 50 cc screw bottle was charged with 40 g of an aqueous alkali solution adjusted to pH 10 by dissolving sodium hydroxide in water, 5.0 g of a water-soluble polymer was added, and the mixture was covered and mixed well. The hydrolysis rate after standing at 50 ° C. for 1 month in an aluminum block heater was evaluated by GC (Gas Chromatography GC-2014, manufactured by Shimadzu Corporation), and judged according to the following criteria.
○: Hydrolysis rate of water-soluble polymer is less than 5% ×: Hydrolysis rate of water-soluble polymer is 5% or more

<Silica dispersibility>
In a 9 cc screw bottle, 0.5 g of a water-soluble polymer aqueous solution having a resin solid content of 20% was added to 5.0 g of colloidal silica (primary particle size: 30 to 50 nm) and mixed well. The particle size (A) of the silica after standing overnight was measured by a dynamic light scattering method (ELSZ-1000, manufactured by Otsuka Electronics Co., Ltd.), and from the particle size (B) of colloidal silica not added with a water-soluble polymer. The rate of change was calculated according to the following formula and judged according to the following criteria.
Rate of change (%) = {(A−B) / B} × 100
○: Change rate is less than 10% Δ: Change rate is 10% to less than 30% ×: Change rate is 30% or more

Production Example 1
≪Synthesis of water-soluble polymer≫
A 5 L four-necked flask equipped with a stirring blade, a reflux condenser, a thermometer, and various introduction tubes was prepared. After charging 1000 parts of pure water, nitrogen was blown from the nitrogen introduction tube at a flow rate of 10 ml / min. The internal temperature was raised to 80 ° C. over 40 min with stirring.
After confirming the temperature rise, an initiator solution prepared by dissolving 2.8 parts of 4,4′-azobis-4-cyanovaleric acid (trade name “ACVA” manufactured by Otsuka Chemical Co., Ltd.) in 30 parts of pure water was added all at once. . After 5 minutes, a monomer aqueous solution prepared by dissolving 700 parts of N-acryloylmorpholine (manufactured by Kojin Co., Ltd., hereinafter referred to as “ACMO”) in 1600 parts of pure water was dropped from the monomer introduction tube over 1 hour to carry out polymerization. In parallel with the monomer aqueous solution, a chain transfer agent aqueous solution in which 1.4 parts of 2-mercaptoethanol (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 140 parts of pure water was dropped from another introduction tube over 1 hour.
After completion of the dropwise addition of each aqueous solution of the monomer and the chain transfer agent, polymerization was further performed at 80 ° C. for 2 hours. Thereafter, the flask was cooled to room temperature, and 0.3 part of 4-methoxyphenol was added to stop the polymerization, thereby obtaining a polymer 1. This polymer 1 had a number average molecular weight (Mn) of 24,000 and a molecular weight distribution (PDI) of 2.4. The polymerization rate calculated from GC was 100%.

Production Example 2
The same operation as in Production Example 1 was carried out except that no chain transfer agent was used, and Polymer 2 was obtained. The Mn of the polymer 2 was 120,000 and the PDI was 3.0. The polymerization rate was 99%.

Production Example 3
Polymer 3 was obtained in the same manner as in Production Example 2 except that the amount of ACVA used as the initiator was changed to 0.5 part. The Mn of the polymer 3 was 250,000 and the PDI was 3.3. The polymerization rate was 99%.

Production Example 4
Polymer 4 was obtained in the same manner as in Production Example 1 except that the monomers used were changed to ACMO 630 parts (82 mol%) and acrylic acid 70 parts (18 mol%). The Mn of the polymer 4 was 25,000 and the PDI was 2.5. The polymerization rate was 99%.

Production Example 5
A polymer 5 was obtained in the same manner as in Production Example 1 except that the monomers used were changed to ACMO 560 parts (60 mol%) and acrylic acid 140 parts (40 mol%). The Mn of the polymer 5 was 25,000 and the PDI was 2.4. The polymerization rate was 99%.

Production Example 6
In Production Example 1, the initiator used was 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate (manufactured by Wako Pure Chemical Industries, Ltd., trade name “VA-”). 046B ") was changed to 0.6 part, and the same operation was performed except that the polymerization temperature was changed to 60 ° C to obtain a polymer 6. The Mn of the polymer 6 was 25,000 and the PDI was 2.5. The polymerization rate was 99%.

Production Example 7
Polymer 7 was obtained in the same manner as in Production Example 1, except that the monomer used was changed to 420 parts (43 mol%) of ACMO and 280 parts (57 mol%) of acrylic acid. The Mn of the polymer 7 was 24,000, and the PDI was 2.4. The polymerization rate was 98%.

Production Example 8
A polymer 8 was obtained in the same manner as in Production Example 1 except that the monomer used was changed to 700 parts of N, N-dimethylacrylamide. The Mn of the polymer 8 was 22,000, and the PDI was 2.2. The polymerization rate was 99%.

The contents and physical properties of each polymer obtained in Production Examples 1 to 8 are shown in Table 1.

Details of the compounds shown in Table 1 are as follows.
ACMO: acryloylmorpholine AA: acrylic acid DMAA: N, N-dimethylacrylamide ACVA: 4,4′-azobis-4-cyanovaleric acid (manufactured by Otsuka Chemical Co., Ltd.)
VA-064B: 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate (manufactured by Wako Pure Chemical Industries, Ltd.)

Example 1
Water was added so that the concentration of the polymer 1 which is a water-soluble polymer was 15% by mass to prepare a semiconductor wetting agent. About the obtained wetting agent for semiconductors, etching resistance, wettability, wafer appearance and alkali resistance were evaluated. The results obtained are shown in Table 2.
Also, 10.0 g of colloidal silica dispersion (primary particle system 30-50 nm, silica solid content 10%) adjusted to pH 10.0 by adding aqueous ammonia and 0.1 g of the above-mentioned wetting agent for semiconductor were added. A composition for an abrasive was obtained. The obtained composition for abrasives was evaluated for silica dispersibility, and Table 2 shows the results.

Example 2
A semiconductor wetting agent and an abrasive composition were prepared in the same manner as in Example 1 except that the polymer 2 was used as the water-soluble polymer, and the same evaluation was performed. The evaluation results obtained are shown in Table 2.

Example 3
A semiconductor wetting agent and an abrasive composition were prepared in the same manner as in Example 1 except that the polymer 3 was used as the water-soluble polymer, and the same evaluation was performed. The evaluation results obtained are shown in Table 2.

Example 4
Water was added so that the concentration of the polymer 1 which is a water-soluble polymer was 10.5% by mass, and a semiconductor wetting agent was prepared. About the obtained wetting agent for semiconductors, etching resistance, wettability, wafer appearance and alkali resistance were evaluated. The results obtained are shown in Table 2.
Moreover, the composition for abrasive | polishing agents was obtained by operation similar to Example 1 using the said semiconductor wetting agent. The obtained composition for abrasives was evaluated for silica dispersibility, and Table 2 shows the results.

Example 5
Water was added so that the concentration of the polymer 1 which is a water-soluble polymer was 4.5% by mass, and a semiconductor wetting agent was prepared. About the obtained wetting agent for semiconductors, etching resistance, wettability, wafer appearance and alkali resistance were evaluated. The results obtained are shown in Table 2.
Moreover, the composition for abrasive | polishing agents was obtained by operation similar to Example 1 using the said semiconductor wetting agent. The obtained composition for abrasives was evaluated for silica dispersibility, and Table 2 shows the results.

Example 6
A semiconductor wetting agent and an abrasive composition were prepared in the same manner as in Example 1 except that 50% of the polymer 1 and 50% of the polymer 2 were used as the water-soluble polymer, and the same evaluation was performed. The evaluation results obtained are shown in Table 2.

Example 7
A semiconductor wetting agent and an abrasive composition were prepared in the same manner as in Example 1 except that the polymer 4 was used as the water-soluble polymer, and the same evaluation was performed. The evaluation results obtained are shown in Table 2.

Example 8
A semiconductor wetting agent and an abrasive composition were prepared in the same manner as in Example 1 except that the polymer 5 was used as the water-soluble polymer, and the same evaluation was performed. The evaluation results obtained are shown in Table 2.

Comparative Example 1
A semiconductor wetting agent and an abrasive composition were prepared in the same manner as in Example 1 except that the polymer 6 was used as the water-soluble polymer, and the same evaluation was performed. The evaluation results obtained are shown in Table 2.

Comparative Example 2
A semiconductor wetting agent and an abrasive composition were prepared in the same manner as in Example 1 except that the polymer 7 was used as the water-soluble polymer, and the same evaluation was performed. The evaluation results obtained are shown in Table 2.

Comparative Example 3
A semiconductor wetting agent and an abrasive composition were prepared in the same manner as in Example 1 except that the polymer 8 was used as the water-soluble polymer, and the same evaluation was performed. The evaluation results obtained are shown in Table 2.

Comparative Example 4
A wetting agent for semiconductor and an abrasive composition were prepared in the same manner as in Example 1 except that hydroxyethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 90,000) was used as the water-soluble polymer. went. The evaluation results obtained are shown in Table 2.

Comparative Example 5
A semiconductor wetting agent and an abrasive composition were prepared in the same manner as in Example 1 except that PVP K30 was used as the water-soluble polymer, and the same evaluation was performed. The evaluation results obtained are shown in Table 2.

Details of the water-soluble polymer shown in Table 2 are as follows.
HEC: hydroxyethyl cellulose (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 90,000)
PVP K30: Polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd.)

Examples 1 to 8 are experimental examples using the water-soluble polymer defined in the present invention, and because the adsorptivity to the wafer is high, results excellent in etching resistance, wettability and appearance on the wafer are obtained. ing. Moreover, it was confirmed that the silica dispersibility is excellent in the case of an abrasive composition. Above all, from the results of Examples 1, 7 and 8 using a water-soluble polymer having the same number average molecular weight and molecular weight distribution, Example 1 comprising 100 mol% of N- (meth) acryloylmorpholine is resistant to etching. The result was excellent, and the appearance on the wafer was also excellent.
On the other hand, Comparative Example 1 using a water-soluble polymer obtained with a cationic polymerization initiator resulted in a greatly inferior silica dispersibility. Moreover, the comparative example 2 using the water-soluble polymer with a small use ratio of N- (meth) acryloylmorpholine was not sufficient in etching resistance and wettability, and was inferior in the appearance of the wafer. Comparative Example 3 is an experimental example using a water-soluble polymer composed of an amide-based compound different from N- (meth) acryloylmorpholine, but the results were greatly inferior in wettability and alkali resistance. Comparative Examples 4 and 5 are examples using cellulose derivatives, which are water-soluble polymers used in conventional polishing compositions, but are satisfactory in terms of adsorptivity to the wafer surface and silica dispersibility. It wasn't.

  Since the wetting agent for semiconductors of the present invention is excellent in the adsorptivity to the wafer surface after polishing, by using a polishing composition containing the wetting agent for semiconductors, the smoothness of the wafer surface after polishing is improved, and , COP can be suppressed. Furthermore, since the dispersibility of silica is also good, it is particularly useful as a composition for final polishing of silicon wafers.

Claims (7)

A wetting agent for polishing silicon wafers, comprising a water-soluble polymer having a structural unit derived from N- (meth) acryloylmorpholine in an amount of 50 to 100 mol% and substantially free of a cationic group. The wetting agent for polishing according to claim 1, wherein a structural unit derived from the N- (meth) acryloylmorpholine is 100 mol%. 3. The polishing wetting agent according to claim 1, wherein the water-soluble polymer has a number average molecular weight in the range of 1,000 to 300,000. The method for producing a water-soluble polymer for polishing a silicon wafer according to any one of claims 1 to 3, wherein a nonionic and / or anionic polymerization initiator is used as a polymerization initiator, and N- ( characterized in that meth) acryloyl morpholine 50-100% and other monomer 0-50 mol% radical polymerization, manufacturing methods. A silicon wafer polishing composition comprising the silicon wafer polishing wetting agent according to claim 1, water, abrasive grains, and an alkali compound.   The polishing composition according to claim 5, which is used for finish polishing of the silicon wafer. A method for polishing a silicon wafer using a water-soluble polymer having a structural unit derived from N- (meth) acryloylmorpholine having 50 to 100 mol% and substantially not containing a cationic group.